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Free Carnitine (Serum)

Published: August 9, 2026Updated: August 16, 2026

This test measures the amount of free carnitine, a compound that helps transport fatty acids into cells for energy production, in your blood serum.

Quick summary

["Free carnitine helps assess metabolic health, especially in conditions affecting fat metabolism."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
53096-4
Short code
C0TOTCSF
Synonyms
Carnitine Free SFr CSF
Category
chemistry
Sample
csf
Container
Sterile CSF collection tubes, screw-cap polypropylene cryovials
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
0–99 years
Method
Tandem Mass Spectrometry (MS/MS) or Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
CPT
82017
SNOMED
104422009
Specimen volume
0.5-1.0 mL of cerebrospinal fluid
Stability
Room temperature: 4 hours; Refrigerated (2-8°C): 24 hours; Frozen (-20°C or below): 30 days for batched analysis. Avoid repeated freeze-thaw cycles.
Hemolysis max
200
TAT
72–168 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms of metabolic disorders, such as muscle weakness, fatigue, or unexplained weight changes. It may also be used to monitor conditions like mitochondrial disorders, carnitine deficiency, or certain genetic metabolic diseases. Doctors might also check it before or after treatments involving medications that affect carnitine levels, such as certain antibiotics or chemotherapy drugs.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to fast for a few hours before the blood draw. Wear a comfortable shirt for easy access to your arm. Avoid strenuous activity the day of the test to ensure accurate results.

During the Test

A healthcare professional will insert a small needle into your arm to draw blood. You may feel a brief pinch, but it usually doesn’t cause significant discomfort. The blood sample is then sent to a lab for analysis.

After the Test

After the blood is drawn, the needle site will be pressed to stop bleeding. You can resume normal activities immediately. There may be a small bruise or redness at the site, but this typically fades within a day or two.

Reference range

Reference values for free carnitine (C0) and total carnitine in CSF are not well established and vary by laboratory. Free carnitine (C0) is typically reported as a ratio to total carnitine. The C0/C-total ratio in CSF is normally >0.9 in healthy individuals. Low ratios may indicate carnitine transporter deficiency or other fatty acid oxidation disorders affecting the central nervous system.N/A

Specimen: csf

No fasting required. CSF collection should be performed by trained personnel via lumbar puncture under sterile conditions. Patient should remain recumbent for at least 1 hour prior to collection if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Low levels of free carnitine can indicate a deficiency, which may be linked to metabolic disorders, poor nutrient absorption, or certain medications. High levels might suggest overproduction of carnitine or conditions affecting its transport, such as kidney disease or certain genetic disorders. Monitoring free carnitine helps diagnose and manage metabolic conditions early for better treatment outcomes.

Short name

Free Carnitine

Frequently asked questions

What does a low free carnitine level mean?
A low free carnitine level may suggest a metabolic issue, such as carnitine deficiency, which can affect how your body uses energy. This could be due to genetic disorders, poor diet, or certain medications. Your doctor may recommend dietary changes, supplements, or further testing to identify the cause and develop a treatment plan.
What causes high free carnitine levels?
High free carnitine levels can occur due to overproduction of carnitine in the body, kidney problems that prevent proper excretion, or certain medications. It may also be seen in conditions affecting fat metabolism. Your healthcare provider will review your symptoms and other test results to determine the underlying cause and guide appropriate management.
Can free carnitine levels change with diet?
Yes, diet can influence carnitine levels. Foods rich in carnitine, such as red meat, fish, and dairy products, may temporarily raise levels. However, long-term dietary changes alone are less likely to significantly alter carnitine status compared to medical interventions. Your doctor may advise specific dietary adjustments if needed for your condition.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy